Wastewater concentrator with plural distributors

ABSTRACT

There is disclosed herein equipment and methods for screening and concentrating wastewater overflow from combined sewer systems and the like. Exemplary equipment includes a separator employing a substantially cylindrical rotating screen. Influent is piped upwardly into the equipment and deflected outwardly by plural distributors toward the inner surface of the screen in a manner to achieve a desired flow rate and flow pattern of the influent onto the screen. Means including the distributors are provided for controlling the flow rate and for suitably directing the influent in a plurality of substantially discrete inclined streams toward the inner surface of the rotating screen. The screen is rotated at a speed to achieve a desired centrifugal force. Effluent passes through the screen to an outlet and the remaining concentrate passes to an outlet. The screen is in the form of a screen cage having a plurality of removable screen panels for facilitating replacement of damaged screens or changing screen type or mesh size. Cleaning means is provided for directing a cleaning fluid periodically at the screen. The methods disclosed involve the manner in which the influent, effluent, concentrate and backsplash are handled, and the manner in which the influent is screened to achieve a fluid concentrate which may be pumpable to other treatment equipment for ultimate disposal.

United States Patent Talley, Jr.

[451 Dec. 26, 1972 [541 WASTEWATER CONCENTRATOR WITH PLURAL DISTRIBUTORS[72] Inventor: Walter J. Talley, Jr., Brentwood Park, Calif.

[73] Assignee: Sweco, Inc., Los Angeles, Calif. [22] Filed: March 19,1971 [21] Appl. No: 126,080

Related US. Application Data [63] Continuation-impart of Ser. No.42,165, June I,

1970, abandoned.

Primary Examiner-Samih N. Zaharna Assistant ExaminerF. F. CalvettiAttorney-Lyon & Lyon [57] ABSTRACT There is disclosed herein equipmentand methods for screening and concentrating wastewater overflow fromcombined sewer systems and the like. Exemplary equipment includes aseparator employing a substantially cylindrical rotating screen.lnfluent is piped upwardly into the equipment and deflected outwardly byplural distributors toward the inner surface of the screen in a mannerto achieve a desired flow rate and flow pattern of the influent onto thescreen. Means including the distributors are provided for controllingthe flow rate and for suitably directing the influent in a plurality ofsubstantially discrete inclined streams toward the inner surface of therotating screen. The screen is rotated at a speed to achieve a desiredcentrifugal force. Effluent passes through the screen to an outlet andthe remaining concentrate passes to an outlet. The screen is in the formof a screen cage having a plurality of removable screen panels forfacilitating replacement of damaged screens or changing screen type ormesh size. Cleaning means is provided for directing a cleaning fluidperiodically at the screen. The methods disclosed involve the manner inwhich the influent, effluent, concentrate and backsplash are handled,and the manner in which the influent is screened to achieve a fluidconcentrate which may be pumpable to other treatment equipment forultimate disposal.

9 Claims, 5 Drawing Figures PATENTED B I972 3.707. 235

sum 3 or 3 I INVENTOR.

I WAATEEJ MALEV WASTEWATER CONCENTRATOR WITH PLURAL DISTRIBUTORS CROSSREFERENCE TO RELATED APPLICATIONS The concepts disclosed herein aredirectly related to those disclosed in applicants co-pending applicationSer. No. 42,165 (now abandoned in favor of Ser. No. 211,763, filed Dec.23, 1971) entitled IMPROVED WASTEWATER CONCENTRATION" filed June 1,1970, of which the present application is a continuation-in-part, thedisclosure of which is incorporated herein by reference. This co-pendingapplication discloses a wastewater concentrator constructed and operatedsimilar to that disclosed herein; however, the present wastewaterconcentrator with plural distributors is an improvement thereoven Theconcepts disclosed herein also are related to those disclosed in US.Pat. No. 3,539,008 entitled SCREENING APPARATUS EMPLOYlNG ROTAT- INGCYLlNDRlCAL SCREEN AND STATIONARY FEED MEANS," and US. Pat. No.3,511,373, both of which are assigned to the assignee of the presentapplication and the disclosures of which are incorporated herein byreference. Briefly, said US. Pat. No. 3,539,008 discloses apparatusinvolving a rotating substantially cylindrical screen in combinationwith a stationary distribution means for screening an influent. Thescreen and distribution means may be used in combination with adownstream planar vibratory separator for further screening of theconcentrate from the rotating screen. Said US. Pat. No. 3,511,373discloses apparatus similar to that of the foregoing patent and isdirected to means for facilitating cleaning of said rotating screen.Reference is also made to related applications, filed concurrentlyherewith, Ser. No. 42,098, now abandoned, entitled UP-FLOW SEPARATOR,"filed in the name of Theodore R. Westfall; Ser. No. 42,099, nowabandoned, entitled IMPROVED ROTATING SCREEN SEPARATOR, tiled in thename of Philip H. Mook; and Ser. No. 42,100, now US. Pat. No. 3,627,130,entitled WASTEWATER CON- CENTRATION," filed in the names of Walter J.Talley, Jr. and Howard W. Wright, Jr. These applications contain asimilar disclosure to that set forth in said application Ser. No.42,165, now abandoned, but include claims directed to various of thestructural and operational features disclosed therein.

BACKGROUND OF THE lNVENTlON This invention relates to the screening of aliquidsolids influent to achieve a desired separation of liquids andsolids, and more particularly to screening of storm water, sewage orstorm water overflow from combined sewer systems and the like.

Although the present inventive concepts are useful in screening variousmaterials, they have particular application for water pollution controland, thus, will be described in this environment and particularly forfinemesh screening for primary treatment of storm water overflow fromcombined sewer systems. As set forth in a research report on treatmentof storm water overflow entitled Rotary Vibratory Fine Screening ofCombined Sewer Overflows prepared by Cornell, Howland, Hayes andMerryfield in connection with Department of the interior Contract14-12-128 and dated March 1970, the majority of the existing combinedsewers throughout the nation do not have adequate capacity during heavystorm periods to transport all waste and storm-caused combined flows toa treatment facility. The overflow is bypassed to a receiving stream,thus causing pollution in the nation s water courses.

As further described in said report, the Federal Water Pollution ControlAdministration published a report in 1967 reviewing the effects andmeans of correcting combined sewer overflows on a national basis Of the200 million people residing in the United States approximately millionare served by combined or separate sewer systems, and of the 125million, approximately 29 percent are served by combined sewers.Combined sewers are designed to receive all types of waste flows,including storm water, for ultimate treatment at a treatment facility.In determining the size of the combined sewer, it has been commonengineering practice to providecapacity for three to five times thedryweather flow. During intensive storm periods, however, thestorm-caused combined flow may be two to 100 times the dry-weather flow,making overflow conditions unavoidable. To compound the problem, mosttreatment facilities are not designed to handle the hydraulic load ofthe combined sewer and, therefore, are required to bypass a portion ofthe storm-caused combined flow to protect the treatment facility andtreatment process from damage. The nations treatment facilities bypassflows an estimated 350 hours during the year, or about 4 percent of thetotal operation time. The pollutional impact of the storm-causedcombined overflow of the waters of the nation has been estimated asequivalent to as much as percent of the strength of the domestic sewagebiochemical oxygen demand. This amount creates a major source ofpollution for the nation 's water courses. The Cornell et al. reportfurther describes certain tests, results and recommendations withrespect to the use of high-rate fine-mesh screens for primary treatmentof storm water overflow from combined sewer systems, the equipmentdescribed being similar to that disclosed in said U.S. Pat. No.3,539,008 and US. Pat. No. 3,511,373.

The present application relates to a wastewater concentrator involvingcertain improvements over those disclosed in said aforementionedapplications and patents. Briefly, the present application is directedto a wastewater concentrator similar to that disclosed in saidco-pending application Ser. No. 42,165, but involves the use of pluraldistributors and a larger screen cage which provides significantlyimproved results in terms of peak hydraulic capacity, substantialreduction of splashback from the screen, increased screen life andperformance at a lower concentrate percentage.

In light of the foregoing, it is a principal object of the presentinvention to provide improved screening equipment.

A further object of this invention is to provide an improved screeningdevice employing a rotating screen and distribution means associatedtherewith.

An additional object of this invention is to provide an improved screendevice employing a rotating screen and plural distribution means forfeeding flows of influent to said screen.

will become apparent through a consideration of the followingdescription and drawings.

SUMMARY OF THE INVENTION There is disclosed herein a screeningapparatus, such as for use in screening of storm water overflows fromsewer systems, comprising a substantially cylindrical rotary screendevice disposed for rotation within a housing, feed means for directingan influent toward the inner surface of the screen, and outlet means forreceiving (a) the effluent which passes through the screen, (b) theconcentrate which does not pass the screen, and (c) backsplash from thescreen.

The feed means includes an upwardly extending feed pipe, or the like,for supplying the influent to plural distributors. In an exemplaryembodiment, two distributors are used, and deflector means areassociated with the feed pipe for deflecting portions of the influent tothe respective distributors which in turn direct the portions ofinfluent toward the inner surface of said screen as a plurality ofsubstantially discrete inclined streams. The deflector means may beadjustable for varying the rate of flow of influent to one or both ofthe distributors.

The rotary screen is in the form of a substantially cylindrical cage andincludes a plurality of screen panels, which may be removed for repair,cleaning or replacement with different mesh screens or different screencloth. The screen panels preferably are square and arranged in two rowswithin the screen cage. The use of square screen panels allows the sameto be removed and repositioned, after rotation of the panel by 90, 180or 270, for equalization of screen wear and thus increased screen life.

The speed of rotation of the screen is selected to provide a desiredcentrifugal force, or g-loading of influent on the screen, the g-loadingbeing a function of the radius of the screen and the square of the rpmthereof. The velocity of flow of influent onto the screen is selectedwithin a preferable range below which suitable impingement does notoccur, and above which excessive splashback and possible screen damagemay occur. A typical flow velocity is in a range around approximately tofeet per second to each distributor, and an exemplary preferred screenspeed is approximately 60 rpm for a 60 inch diameter screen, it beingappreciated that other suitable flow velocities, screen speeds,diameters, and the like may be employed without departing from thepresent concepts. The influent preferably is screened to achieve arelatively fluid concentrate, as distinguished from a dry concentrate,so that the same may be readily transported or pumped for furthertreatment or disposal.

A screen cleaning apparatus may be provided for spraying cleaning fluidthrough the screen at desired intervals as described in said applicationSer. No. 42,165.

4 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectionalelevational view of a preferred screening apparatus according to thepresent invention;

FIG. 2 is a perspective view of a double distributor of the apparatus ofFIG. 1;

FIG. 3 is a partial perspective view of a rotary screen cage of theapparatus of FIG. 1;

FIG. 4 is a graph depicting exemplarly hydraulic split vs. solidsloading; and

FIG. 5 is a partial view of a deflector of the apparatus of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS Turning now to the drawings, andparticularly to FIG. 1, a rotary screening device is illustratedincluding an outer substantially cylindrical housing 10 containing arotary screen cage 11, and influent feed pipe means 12 and twodistribution domes or distributors I3 and 14 for supplying influenttoward the inner surface of the screen cage 11. The device also includesan effluent outlet 15, a concentrate outlet 16, and a backsplash outlet17. A drive assembly 18 is provided for rotating the screen cage 11. Thefeed pipe means 12 includes an inlet pipe 19 and a smaller coaxiallymounted pipe 20. impingement plates or diverters 21 and 22 are providedfor respectively deflecting influent from the pipe 19 to the distributorI3 and from the pipe 20 to the distributor 14.

As will be more fully explained subsequently, an influent, such as stormwater overflow having enormous amounts of water and relatively littlesolids, is fed to the feed pipe means 12 and deflected downwardly andoutwardly by the impingement plates 21 and 22 to the dis tributors l3and 14, and outwardly therefrom toward the inside of the rotating screencage 11. The screen cage includes a plurality of screen panels, and theinfluent is screened resulting in a highly liquid effluent and aflowable concentrate. The effluent is discharged by outlet 15 and theconcentrate is discharged by outlet 16. The screen cage 11 is rotated ata speed to provide a suitable centrifugal force for the screeningaction, and the impingement plates 21 and 22 are positioned to providethe desired flow rate of influent toward the screen cage. Thedistributors l3 and 14 in combination with the plates 21 and 22, areprovided to direct the influent as a plurality of substantially discreteinclined flows toward the inner surface of the screen cage.

These screening concepts serve to reduce pollution caused, for example,by overflow of combined stormsanitary sewage systems during periods ofheavy rain fall. As much as one third of the sewage solids settle to thebottom of large combined sewers and in periods of heavy rain, they flowinto streams, lakes, rivers and coastal waters without treatment. Thus,during storm peaks, up to percent of the untreated sanitary sewage mayoverflow into receiving waters. As a result, combined treatment systemsoften lose more pollutants to their rivers and streams than they takeout in the treatment plant itself.

As will appear from the following description and drawings, the presentapparatus and concepts meet many storm-sanitary pollution controlrequirements for a compact, low cost, high volume, primary treatingsystem. The present apparatus is capable of relieving a combined sewagesystem of its hydraulic overload during storm periods, while sending apollutant concentrate to the treatment plant.

Exemplary apparatus is approximately 7 feet in diameter and 6% feethigh, and employs two rows of square screen panels on the revolvingscreen case, with each row having 18 panels approximately inches square.A combination of influent flow velocity and centrifugal force can allowapproximately 90 to 95 percent of a hydraulic flow of 3 to 4 milliongallons per day to pass through the screens. The remaining concentratecontaining a high percentage, such as 99 percent, of the floatable andsettleable solids is discharged separately into the hydraulicallyrelieved sewage system.

Considering the construction of the apparatus in more detail, thehousing 10 includes a base 24, a substantially cylindrical upstandingwall 25, and a top cover 26 to provide a substantially closed container.The screen drive assembly 18 may be mounted within a housing 27 on thetop of the apparatus, and includes a motor 29 and gear box 30 suitablymounted for driving a drive pulley 31 by means of V-belts 32 and 33. Apair of bearings 34 and 35 are suitably mounted on top of the apparatus,and a shaft 36 is journaled in the bearings 34 and 35 and coupled to thedrive pulley 31. The drive shaft 36 has a collar 37 secured thereto, asby welding. A central collar 38 affixed to the screen cage 11 is boltedto the collar 37 to enable the shaft 36 to rotate the screen cage.

The cover 26 may be a lift-off cover, if desired, to enable access tothe interior of the apparatus. The wall 21 of the housing 10 may includea window 41 for observation of the interior of the apparatus. Suitablebracing is provided within the housing for structural purposes and forfirmly supporting the various pipes. An angle bracket 42 and braces 43,for example, are provided as illustrated in FIG. 1 to secure the variouscomponents within the housing.

The screen cage 11 will be described in more detail subsequently, butgenerally includes a cage formed of a lower angle ring 46, an upper barring 47, and a plurality of upstanding bars 48 extending between theangle ring 46 and bar ring 47 as best seen in FIG. 3. Eighteen bars 48have been used for an exemplary cage approximately 60 inches indiameter. Support ribs 50 are connected between the various bars 48 andthe central collar 38 which is secured to the collar 37 affixed to theshaft 36 as noted earlier. Removable screen panels 52 and 53 having aframe and screening material of metal or cloth secured thereto areinserted in two rows between the vertical bars 48 and clamped thereto ina substantially sealed relationship.

As noted previously, an influent to be screened is supplied through theinfluent pipe 12 and directed upwardly through the pipes 19 and towardthe impingement plates 21 and 22. The plates deflect the flow to thedistributors l3 and 14 and from there out wardly toward the innersurface of the screen panels 52 and 53 of the screen cage 11. Thevertical position of the plates 21 and 22 are adjustable as will beexplained subsequently so as to control the rate of flow of influent.The lower distributor 13 is secured in a suitable manner to the upperend of the pipe 19. This distributor 13 may include a central sleeve 60secured, as by welding, to the pipe 19, and includes a plurality ofinclined plates 62 secured to the outer surface of the sleeve 60. Aportion 63 of each plate 62 may be bent upwardly as shown in FIG. 2, orseparate spacers may form the portions 63, and be secured to theunderside of the next succeeding plate so as to form a rigid structure.

The upper distributor 14 may be constructed in a similar manner of acentral sleeve, which may be formed by the pipe 20, and a plurality ofinclined plates 64 secured to the outer surface of the pipe 20. Aportion 65 of each plate 64 may be bent upwardly as shown in FIG. 2 andbe secured to the underside of the next succeeding plate 64 so as toform a rigid structure as is the case with the distributor 13. The upperdistributor 14 may be secured in any suitable manner, such as by meansof vertical spacer rods 66 as seen in FIGS. 1 and 2, or, alternatively,the pipes 19 and 20 may be secured together as by gussets, so as to forma rigid structure of the two distributors 13 and 14. If desired, thespacers 66 may be threaded to enable adjustment of the spacing betweenthe two distributors 13 and 14.

The lower impingement plate 21 may be coupled to the pipe 20 by means ofa flange 68 affixed to the periphery of the pipe and bolts 69. Thisarrangement allows adjustment of the position of the plate 21 withrespect to the upper end of the pipe 19, and thus adjustment of the rateof flow of influent to the lower distributor 14. The upper impingementplate 20 may be secured to a rod 70 which extends upwardly through theshaft 36. The upper end of the rod 70 may be threaded into a threadedbushing 71 which is secured to the upper end of the shaft 36. The rod 70thus may be adjusted up or down to vary the position of the plate 22with respect to the upper end of the pipe 20, and may be locked inposition by a locknut 72. With this an rangement, the plate 22 rotateswith the screen cage 11, but may be made stationary if desired by othersuitable supporting structure. Both of the impingement plates 21 and 22may have respective downwardly extending lips 74 and 75 for providingbetter deflection of the influent toward the distributors 13 and 14 Thedistributors 13 and 14 function to direct influent, which has beendeflected by respective impingement plates 21 and 22, into substantiallyinclined streams toward the inner surface of the screen panels 52 and53.

An interior wall or divider 76, which is substantially cylindrical, issecured within the housing and extends almost up to the horizontalsurface of the flange of the angle ring 46. This divider forms, incombination with the housing wall 25, an annular chamber 77 forreceiving effluent and directing the same to the effluent outlet 15. Theeffluent, as is known to those skilled in the art, is the material whichpasses through the screen panels in the screen cage 11. The divider 76also encloses a concentrate chamber or bowl 78 which has an inclinedbottom 79 for directing concentrate to the concentrate outlet 16.

A backsplash pan 81 may be used and positioned within the chamber 78 andcoupled with a support 82. The pipe 17 communicates with the interior ofthe pan 81. The top of the pan 81 is approximately at the elevation ofthe bottom of the screen panels and the radius of the upper portion ofthe pan 81 is slightly smaller than the interior diameter of the screencage 11 so as to receive any influent which may splash back from theinner surface of the screen cage 11 and screen panels. The radius of thepan 81 typically may be about 2 inches less than the radius of thescreen cage 11. Concentrate flows through the gap between the interiorof the cage 11 and the exterior of the pan 81 to the chamber 78. Thepurpose of the backsplash pan 81 is to enable any influent whichsplashes from the screen cage 11 to be collected for either recyclingwith incoming influent or sent to another separator device for screeningto ensure that the maximum desired split between effluent andconcentrate is achieved. However, through the use of plural distributorsand a lower feed velocity of influent toward the screen panels, it hasbeen discovered that such backsplash found in earlier devices is almosteliminated.

Turning again to the influent impingement plates 21 and 22, the same areadjustable up and down as noted earlier. The purpose of this adjustmentis to enable control of an orifice area 85 between the impingement plate21 and the upper end of the pipe 19. A partial detailed view of thisplate 21 is shown in FIG. 5, and the same includes an invertedfrusto-conical member 87 which acts, in combination with the top edge ofthe pipe 19, to form the adjustable orifice area 85. Similarly, theorifice area 86 between the lower surface of the plate 22 and upper endof the pipe 20 can be controlled or varied. This arrangement allowscontrol of the split of influent between the two distributors 13 and 14as well as control of the rate of flow of influent toward the screenpanels. The plates 21 and 22 may have other shapes, such as a segment ofa sphere. However, it is desired that the flows of influent toward theinner surface of the screen cage 11 from distributors 13 and 14 besubstantially perpendicular (as viewed in FIG. I) to the inner surfaceof the screen panel 52 and 53 rather than significantly inclinedupwardly or downwardly. If these flows are sharply inclined downwardly,the concentrate is excessively liquid; but, on the other hand, if theflows are precisely horizontal and thus perpendicular to the innersurface of the screen panels, the flows do not fan out sufficiently togive a wide sweeping flow onto the inner surface of the screen panels.Accordingly, it is desired that the flow of influent be almostperpendicular to the inner surface of the screen panels but at a slightdownward angle to obtain a divergent flow, or fan-out of the flow, bythe time the influent hits the screen panels. Each flow of influent froma distributor should fan out to anywhere from substantially the entireheight of the respective row of screen panels to approximately one-halfthe height of the row of screen panels, or slightly less, such as toprovide an impingement area of influent onto the screen panels about 6inches high. That is, the inclined flows from distributor 13 shouldfan-out and cover a height of about 6 inches of the approximately inchhigh panels 53. The same is true for the flows from distributor 14.Thus, it is desired that the flows fan-out slightly, but still flowsubstantially horizontally from the orifices 85 and 86, the fanning-outbeing accomplished by the respective distributors l3 and 14 into twogroups of essentially discrete inclined streams. If only a portion ofthe height of the screen panels is swept by the influent flows, thepanels can be turned over end-for-end or 90 after a period of use tomaximize screen life.

As discussed earlier, the majority of the existing combined sewersthroughout the nation do not have adequate capacity during heavy stormperiods to transport all waste and storm-caused combined flows to atreatment facility. The overflow is bypassed to a receiving stream, thuscausing pollution problems. One of the principal applications of thepresent apparatus is in screening enormous amounts of water with solids,such as storm overflow, to separate out the solids and provide arelatively fluid, as distinguished from dry, concentrate which can thenbe properly handled by a sewage treatment facility. The effluent can besuitably disposed of, as for example in a stream or applied to secondarytreatment. In this manner, the enormous amounts of water do not overtaxthe sewage treatment facility, while still enabling proper treatment ofthe maximum amount of solids from the overflow.

One of the principal objectives is to achieve a high split, that is,ratio of effluent (screened product) to concentrate (unscreenedproduct), while still obtaining a slightly fluid concentrate which canflow continuously from the apparatus and be supplied, as by pumping, tosubsequent primary treatment equipment without the problems involved inhandling a solids concentrate. A typical ratio is better than 90 to 10with the apparatus described herein and with a typical influent flow ofabout 2500 gallons per minute. A number of factors affect this split,one of the principal factors being the centrifugal force involved in thescreening operation, which varies as the square of the screen cage rpmand as a direct function of the radius thereof. There is a band ofoptimum performance in terms of centrifugal force. it has been foundthat a centrifugal force of around 3 gs appear to be optimum in achiev'ing the maximum split, although it is to be understood that the forcecan be below or above this value somewhat. This approximate force orband around 3 gs can be obtained with a screen cage speed ofapproximately 60 rpm for a screen cage about 60 inches in diameter, oralternatively approximately 88 rpm for a screen cage about 36 inches indiameter. Substantially higher speeds do not improve the split and canactually degrade the split. Additionally other factors are important inachieving the maximum split, and these include the velocity of the feedof influent, such as approximately 5 to 10 feet per second to eachdistributor, which can be selected by varying the size of the orificesand 86 through adjustment of the plates 21 and 22; directing of theflows of influent substantially perpendicular to the inner surface ofthe screen cage as noted earlier; maintaining the screen panels clean;the orientation of the screen cloth in the screen panels; and recyclingor other screening of backsplash from the screen cage.

The centrifugal force is important in achieving the maximum force on thesolid and water particles for separation of the water from the solids,but must not be excessive because the solids will then tend to cling tothe screen and blind or clog the screen and, additionally, screen damagemay result from high forces. At the optimum force or band of force, theconcentrate flows by gravity down from the screen. The provision ofalmost perpendicular flows to the inner surface of the screen isimportant as noted earlier so as to achieve the maximum separation withthe minimum of backsplash or other deflection of influent from thescreen cage. As

fluent reaches the screen. If too high, too much influent reaches thescreen and excessive backsplash may occur, and the high forces may causepremature blinding of the screen and/or damage thereto. The backsplashrepresents unscreened influent, much of which is believed to bedeflected from the bars 48 of the screen cage, and the backsplash can berecycled or otherwise further screened to optimize the split. It will beapparent that the screen panels must be clean to achieve the bestscreening action, and a cycle of influent feed and spray cleaning with acleaning fluid is preferred as described in application Ser. No. 42,165.The orientation of the screen cloth within the cage is important from awear-life standpoint. It is preferable that the screen cloth be biasmounted, as described in said lastnamed application, to form the screenpanels rather than positioning the cloth such that the wires or threadof the screen cloth run vertically and horizontally. The bias mountingdisposes the wires or thread at substantially 45 angles resulting inbetter screen life because the screen wires are stressed and flexedequally and uniformly by the flows of influent. This longer life allowsthe screen cage to run longer with less down-time therefore improvingthe efficiency of screening. Also,

the slope of the inclined plates 62 and 64 of the distributors 13 and 14affects the height of which the flows impinge on the screen panels and,thus affects screen life. A 6 inch drop at the edge of the plate wherethe radial length of the plate is 28 inches gives a slope of 21 percentwhich has been found suitable for a 60 inch diameter cage.

Furthermore, it is believed that the direction of rotation of the screencage with respect to the inclination of the plates 62 and 64 maycontribute to obtaining the most efficient screening operation. Thedirection of rotation of the screen cage 11 is preferably as indicatedin FIG. 2 (counter clockwise). The flows of influent leave the inclinedplates 62 and 64 at substantially the angle of the plates 62 and 64 andare believed to aid in sweeping large solid particles from the rotatingscreen.

Screen cleaning is achieved by means of supply pipes 90 and 91 havingrespective groups of nozzles 92 and 93. The nozzles provide sprays ofcleaning fluid through the screen panels. it is desired to clean thescreens before they get dirty which can be measured in terms ofdegradation of the split, for example, down to 90-to-l0.

Turning again to the screen cage, and particularly FIG. 3, preferablythe screen panels 52 and 53 are square and arranged in upper and lowerrows as shown. it is also desirable that they be removable for repair orreplacement and can be readily locked in place in the screen cage.Channels for receiving the side edges of the screen panels 52 and 53 areprovided by T-brackets 95 which are secured to the bars 48 by threadedstubs 96 and 97 and respective wing-nuts 98 and 99. Braces 101 aresecured between adjacent ribs 50, and a gasket 102 is affixed onto eachbrace 101 to form a seal with the top of each respective upper screenpanel 52. The side edges of the frame of each screen panel which abutswith the bars 48 may have a bead of resilient material thereon to form aseal between the screen panels and bars 48. A similar bead of materialcan be used between the lower edge of the frame of panel 52 and upperedge of the frame of panel 53. Each panel includes an angle frame 104and the screen fabric 105 may be secured thereto with an epoxy adhesive.Exemplary screen fabric is 165 TBC providing 47 percent open area. Metalor synthetic fabrics can be used. Stainless steel fabric has been foundsuitable. A removable cover 106 may be provided for the top of thescreen cage.

The interior of the housing 10 may be vented to the atmosphere. A plate108 may be attached to the shaft 36 above the cover portions 26 and 27of the housing. Operation of the screening apparatus causes a higherpressure area toward the periphery of the screen cage 11, and air isdrawn in between the plate 108 and cover portions 26-27. This flow ofair past the plate 108 can aid in maintaining the bearings 34 and 35clean and moisture free. The plate 108 prevents material from splashingonto the bearings from the cover portion 26-27 where the shaft 36extends therethrough.

The following represent exemplary test data for apparatus as describedherein, and as referred to below as a 21 inch deep (high) screen cagewith double distributor unit. This unit involved a screen cage ofapproximately inches in diameter and approximately 21 inches high withtwo rows of approximately 10% inch square screen panels, with IS panelsin each row. Reference to a 16 inch deep screen cage with singledistributor unit refers to a similar unit as more particularly describedin said application Ser. No. 42,165, involving a single distributor andan approximately 60 inch diameter screen cage having a height ofapproximately 16 inches.

Tests as indicated in Table I below provide a basic comparison betweenthe l6 inch and 21 inch units. These tests were performed with influentof clear tap water and then with influent containing paper pulpsolutions at two separate concentration levels. The paper pulp solutionswere made up in a 1300 gallon stock tank employed in conjunction with ahydraulic test stand, and these solutions were re-circulated through theunit. in the test stand operation, influent was continuously pumped intothe unit from the stock stank. The unit separates this influent into theeffluent, concentrate and splashback streams which were all measured andre-circulated directly back into the stock tank. This enables asteady-state evaluation of the units to be made. The performance of eachunit is set forth in Table I below.

TAB LE 1 Combined (oncow Hydraulic Splasliruma, plus Combined tram,split, bat-k, splash, split. Unit influent apm. pun-nut ppm. g.p.|n.litl't'lilll.

(lean water, 2,!00 gpnuum. 3.57 35 WI 5.23 16" deep screen (age withsingle distributor i ..{ll7 ppm. paper pulp, 2.1m) apin... 143 6.81) 3517s H. 47 234 ppm. paper pulp. 13,100 ppm 220 Ill. -17 3.5 255 111i(lt'all water, 2.100 ppm [l2 5.33 T llll 5.6" 21"decp scrum! cag withrioulslo distributor... v.{lli' ppm. paper pulp, .',|nl)ii mum... lfiti7. 42 T 163 7. 7 1 2341).]Ll1l. paper pulp, Lilli) L'.|].ll| 200 l. 52 7.307 1.35

Additional tests on the 21 inch unit with the double distributor weremade. These tests were performed with a re-circulating solutioncontaining approximately 234 parts per million (ppm) by weight of paperpulp, and are set forth below.

Case No. l The deflector 22 for the top distributor 14 was adjusted toits fully raised position (approximately 2 inches above distributor 14).The deflector 21 for the bottom distributor 13 was adjusted verticallyso that there was a 58-inch clearance between the outermost lower lip ofthe deflector and the top of the distributor. The influent to the unitwas 2,100 GPM; the concentrate flow measured 210 GPM; the splashbackflow measured 7 GPM; and the effluent flow, by the difference, may betaken as 1,883; the hydraulic split was 10.0 percent.

Case No. 2 With the bottom deflector 21 in the same position as for theprevious case but with the top deflector 22 moved down 1 inch toward thetop distributor, the influent flow remained 2,100 GPM; the concentrateflow became 170 GPM; the splashback remained 7 GPM; and the effluent,again by difference, was 1,923; the split was 8.1 percent.

GPM; the effluent, by difference, was 1,352; and the split was 8.0percent.

Case No. 6 With other conditions the same as Cases Nos. 4 and 5, thetotal influent was reduced to 1,000 GPM; the concentrate became PGM; thesplashback reduced to 22 GPM; the effluent, by difference, was 903 GPM;and the split was 8.1 percent.

Case No. 7 With the top deflector 22 still lowered 1 inch from itsmaximum up position, the bottom deflector 21 was placed in service butwas lowered with references to Cases Nos. 1 and 2. The bottom apex 107(FIG. 5) of the cone 87 of the lower deflector 21 was placed one-eighthinch above the top of the pipe 19 associated with the lower distributor13. With the bottom deflector 21 in this position, the influent wasmeasured at 2,050 GPM; the concentrate measured 160 GPM; the splashbackmeasured 7.6 GPM; the effluent, by difference, was 1,882 GPM; and thesplit was 7.8 percent. A comparison of Case No. 4 with Case No. 7indicates that the increased screen area in the cage under testcontributes significantly to the overall performance.

Table 11 below provides a summary of Cases 1 through 7 above.

TABLE I1 Eflfluont Combined Concrn- Splas11- (by (111- Hydraulic cone.plus Combined November 24 test lnlluent, trato, back, ferenca), 5 it,splash, s it, ronditions ppm. g.p.m. 51.1mm. g.p.m. percent gpni.porn-n1.

("rrsi-luuwflflun. 2,100 210 7 1,883 10.0 217 10.3 (ass 2 2, 100 170 71,023 8.1 177 B. 1 C 11.80 3 2, 100 100 30 1, S .1. 2 220 10. 5 Cast 42,100 160 30 1,010 7. T 51. (I (1ase5 1,500 118 30 1,352 8.11 148 0.0Case 0 1,000 75 22 .103 8. 1 J? l). 7 (Jase 7 2, 050 7.11 1,882 7. 8 1688. 2

Case No. 3 With the bottom deflector 21 35 Case No. 8 With the machineadjusted as in Case completely closed off so that fluid flow wasprevented on the bottom distributor l3 and with the top deflector 22raised to its original Case No. 1 position so that all of the influentwas sent over the top distributor 14 only, the influent measured 2,100GPM; the concentrate measured 190 GPM; the splashback increased to 30GPM; the effluent, again by difference, was 1,880; and

No. 7, additional paper pulp was incrementally added to therecirculating test stand fluid. This gave a measure of performance ofthe unit as a function of influent solids loading, other conditionsbeing held constant.

0 Table [11 below gives the results of this test. P16. 4 is a graph ofhydraulic split vs. paper pulp loading for Case No. 8.

TABLE I11 l.p.|n.

paper ivy (1.11.111. (.1.p.m. Hydraulic Combined Sam p10 referent-rwright. in Ur.p.1n. conceit splashsplit, split number influent. influentirate hat-.1; pllt'l llt prrel nt 2315 l, 050 164 7. 6 8. 0 8. 3 321 2.050 T. 6 .1. 0 .I. 4 4001 J, 100 212 7. 5 10. 1 10. 5 101 l, 100 240 7.5 11. 4 11. t lilil 2, 1.00 250 8. Ii 13. 3 13. 8 831 2,100 320 x. )s15. 2 15. 7 1, 000 2, 100 340 .l. 5 10. J 11'). 7 1, 310 2, 100 375 10.3 17. .J is. 3 1, 701 2, 100 425 12. 0 20. 2 20. b 2, 11 8 2,100 530 13.3 25. 2 25. .l .I, 100 570 16. 7 .27. l 28. 0

It was observed that the hydraulic split did not deteriorate with timeduring periods between cleaning cycles. That is, in the absence ofgrease, the hydraulic split on paper pulp solution appeared to dependupon influent solids loading and to remain constant at a given value forvery long periods.

When evaluating this data, it is believed helpful to combine theconcentrate with the splashback in order to arrive at a figure for allthat material which does not go through the screens and to compare thistotal with the effluent which does go through the screens in order toarrive at a value for combined hydraulic split. Accordingly, the tablesinclude the value for combined split computed on this basis.

Although exemplary apparatus in accordance with the present inventionhas been described herein as including two distributors and deflectors,a larger number of the same may be used to increase the hydrauliccapacity of the unit. Although an exemplary unit having a diameter ofapproximately 60 inches and 21 inches high has been described, differentsizes may be employed. Likewise, a different number of rows of screenpanels and different numbers of panels per row may be used. Theexemplary apparatus had a l4 inch diameter pipe l9, inch diameter pipe20, approximately 17% inch diameter plates 21 and 22, approximately 10%inch square panels 52 and 53, and an approximately 0-% inch spacingbetween the distributors 13 and 14 at the center aperture thereof.

The present embodiments of this invention are to be considered in allrespects as illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims therefore are intended to be embraced therein.

What is claimed is:

1. Screening apparatus comprising support means, and a rotarysubstantially cylindrical screen structure supported by said supportmeans; drive means coupled with said screen structure for rotating saidscreen structure,

distributor means supported by said support means and disposed withinsaid screen structure for feeding influent to be screened toward theinner surface of said screen structure, said distributor meanscomprising at least two vertically spaced distributors for feeding atleast two respective vertically spaced groups of influent each as aplurality of substantially discrete streams on and around said innersurface of said screen structure and inclined with respect to the axisthereof, and

feed means extending upwardly into said screen structure for feedinginfluent to said distributor means, said feed means including pipe meansfor receiving influent from a source of influent and deflector meanspositioned with respect to said pipe means for proportioning theinfluent and deflecting the same downwardly onto said respec tivedistributors to form said groups of influent fed onto said inner surfaceof said screen structure.

2. Screening apparatus as in claim 1 wherein said feed means includes afirst pipe member for receiving said influent and supplying a portion ofsaid influent to a first of said distributors, and includes a secondpipe member for receiving a portion of said influent and feeding saidlatter portion to a second of said distributors, and said deflectormeans includes adjustable deflectors mounted with respect to said firstand second pipe members to allow proportioning of the flow of influentonto said distributors.

3. Screening apparatus as in claim 2 wherein said second pipe member iscoaxially mounted within said first pipe member, and the first of saiddeflectors is mounted adjacent an upper end of said first pipe memberfor deflecting a portion of influent downwardly toward the first of saiddistributors, and said second deflector is mounted adjacent an upper endof said second pipe means for feeding another portion of said influentdownwardly toward the second of said distributors.

4. Screening apparatus as in claim 1 wherein each of the saiddistributors includes a plurality of inclined plates for forming saidinclined streams of influent fed onto said inner surface of said screenstructure.

5. Screening apparatus as in claim 1 wherein said screen structureincludes a frame having disposed therein a plurality of screen panels,said screen panels being arranged in rows one above the other, each rowreceiving influent from a respective distributor.

6. Screening apparatus comprising support means, and a rotarysubstantially cylindrical screen structure having a plurality of screenpanels therein, said screen structure being supported by said supportmeans,

drive means coupled with said screen structure for rotating said screenstructure,

distributor means supported by said support means and disposed withinsaid screen structure for feeding influent toward the inner surface ofsaid screen structure, said distributor means comprising at least twovertically spaced distributors for feeding at least two respectivevertically spaced groups of influent each as a plurality ofsubstantially discrete inclined streams on and around said inner surfaceof said screen structure, each of said distributors including aplurality of inclined plates for directing said inclined streams ontosaid inner surface of said screen structure at an angle with respect tothe axis thereof, and

feed means extending upwardly into said screen structure for feedinginfluent to said distributor means, said feed means including pipe meansfor receiving influent from a source of influent, and said feed meansincluding deflectors adjustably positionable with respect to said pipemeans for proportioning the influent and deflecting the same downwardlyonto said respective distributors to form said groups of influent fedonto said inner surface of said screen structure.

7. Screening apparatus as in claim 6 wherein the flow rate of each groupof influent is proportionable by said deflectors within a range ofapproximately 5 to 10 feet per second.

8. Screening apparatus as in claim 7 wherein said screen structure has adiameter of approximately 5 feet.

9. Screening apparatus comprising a rotary substantially cylindricalscreen structure,

drive means coupled with said screen structure for rotating said screenstructure,

stationary distributor means disposed within said screen structure forfeeding influent to be screened toward the inner surface of said screenstructure, said distributor means including at leasttraitsa'izciisattsiaarsssg'assess; at least two respective verticallyspaced groups of influent each as a plurality of substantially discretestreams onto said inner surface of said screen structure with saidstreams being inclined with respect to the axis thereof, and

feed means extending upwardly into said screen structure for feedinginfluent to said distributor means, said feed means including a firstpipe for second deflector means adjustably positionable receivinginfluent from a source of influent and with respect to an upper end ofsaid second pipe cooperating with a lower of said distributors and fordeflecting influent downwardly onto an upper including deflector meansadjustably positionable one of said distributors, said pipes anddeflector with respect to an upper end of said first pipe for meansenabling proportioning of said influent onto deflecting influentdownwardly onto said lower of said distributors and formation of saidgroups of said distributors, and said feed means including a influent.second pipe coaxially mounted with respect to said a a a u a first pipefor receiving influent and including

1. Screening apparatus comprising support means, and a rotarysubstantially cylindrical screen structure supported by said supportmeans; drive means coupled with said screen structure for rotating saidscreen structure, distributor means supported by said support means anddisposed within said screen structure for feeding influent to bescreened toward the inner surface of said screen structure, saiddistributor means comprising at least two vertically spaced distributorsfor feeding at least two respective vertically spaced groups of influenteach as a plurality of substantially discrete streams on and around saidinner surface of said screen structure and inclined with respect to theaxis thereof, and feed means extending upwardly into said screenstructure for feeding influent to said distributor means, said feedmeans including pipe means for receiving influent from a source ofinfluent and deflector means positioned with respect to said pipe meansfor proportioning the influent and deflecting the same downwardly ontosaid respective distributors to form said groups of influent fed ontosaid inner surface of said screen structure.
 2. Screening apparatus asin claim 1 wherein said feed means includes a first pipe member forreceiving said influent and supplying a portion of said influent to afirst of said distributors, and includes a second pipe member forreceiving a portion of said influent and feeding said latter portion toa second of said distributors, and said deflector means includesadjustable deflectors mounted with respect to said first and second pipemembers to allow proportioning of the flow of influent onto saiddistributors.
 3. Screening apparatus as in claim 2 wherein said secondpipe member is coaxially mounted within said first pipe member, and thefirst of said deflectors is mounted adjacent an upper end of said firstpipe member for deflecting a portion of influent downwardly toward thefirst of said distributors, and said second deflector is mountedadjacent an upper end of said second pipe means for feeding anotherportion of said influent downwardly toward the second of saiddistributors.
 4. Screening apparatus as in claim 1 wherein each of thesaid distributors includes a plurality of inclined plates for formingsaid inclined streams of influent fed onto said inner surface of saidscreen structure.
 5. Screening apparatus as in claim 1 wherein saidscreen structure includes a frame having disposed therein a plurality ofscreen panels, said screen panels being arranged in rows one above theother, each row receiving influent from a respective distributor. 6.Screening apparatus comprising support means, and a rotary substantialLycylindrical screen structure having a plurality of screen panelstherein, said screen structure being supported by said support means,drive means coupled with said screen structure for rotating said screenstructure, distributor means supported by said support means anddisposed within said screen structure for feeding influent toward theinner surface of said screen structure, said distributor meanscomprising at least two vertically spaced distributors for feeding atleast two respective vertically spaced groups of influent each as aplurality of substantially discrete inclined streams on and around saidinner surface of said screen structure, each of said distributorsincluding a plurality of inclined plates for directing said inclinedstreams onto said inner surface of said screen structure at an anglewith respect to the axis thereof, and feed means extending upwardly intosaid screen structure for feeding influent to said distributor means,said feed means including pipe means for receiving influent from asource of influent, and said feed means including deflectors adjustablypositionable with respect to said pipe means for proportioning theinfluent and deflecting the same downwardly onto said respectivedistributors to form said groups of influent fed onto said inner surfaceof said screen structure.
 7. Screening apparatus as in claim 6 whereinthe flow rate of each group of influent is proportionable by saiddeflectors within a range of approximately 5 to 10 feet per second. 8.Screening apparatus as in claim 7 wherein said screen structure has adiameter of approximately 5 feet.
 9. Screening apparatus comprising arotary substantially cylindrical screen structure, drive means coupledwith said screen structure for rotating said screen structure,stationary distributor means disposed within said screen structure forfeeding influent to be screened toward the inner surface of said screenstructure, said distributor means including at least two verticallyspaced distributors each including a plurality of inclined plates forforming and feeding at least two respective vertically spaced groups ofinfluent each as a plurality of substantially discrete streams onto saidinner surface of said screen structure with said streams being inclinedwith respect to the axis thereof, and feed means extending upwardly intosaid screen structure for feeding influent to said distributor means,said feed means including a first pipe for receiving influent from asource of influent and cooperating with a lower of said distributors andincluding deflector means adjustably positionable with respect to anupper end of said first pipe for deflecting influent downwardly ontosaid lower of said distributors, and said feed means including a secondpipe coaxially mounted with respect to said first pipe for receivinginfluent and including second deflector means adjustably positionablewith respect to an upper end of said second pipe for deflecting influentdownwardly onto an upper one of said distributors, said pipes anddeflector means enabling proportioning of said influent onto saiddistributors and formation of said groups of influent.